Adding an image in the image editor through python
Color is a parameter of bpy.ops.image.new():

bpy.ops.image.new(name="Untitled", width=1024, height=1024, color=(0.0, 0.0, 0.0, 1.0), alpha=True, generated_type='BLANK', float=False, gen_context='NONE', use_stereo_3d=False)


bpy.ops.image.new in API